This invention relates in general to a passive restraining system for occupants of a vehicle and, in particular to a restraining system using air bags for protecting the front seat occupants of a vehicle in a low speed collision.
In German Publication DE-OS No. 27 45 620, a restraining system is known for having air bags for the driver and the front seat passenger which are inflatable in the event of a collision. The air bags are inflated in a controlled manner by output signals of a sensor system which are based upon the change in speed of a vehicle. In the event of an accident, the air bag on the passenger side can be inflated when the vehicle speed is within a first lower threshold value S1, corresponding to an equivalent test speed of between 7.5 and 11.2 mph (12 and 18 kph). The air bag on the driver side, however, cannot be inflated unless the vehicle speed is within a second higher threshold value S2, corresponding to an equivalent test speed of between 11.2 and 15.5 mph (18 and 25 kph). Thus, in accidents occurring at speeds at the first lower threshold value, only the passenger of the vehicle and not the driver, is protected by the air bag system.
Using seat belts, with or without belt tighteners, in combination with an air bag restraining system, provides the occupants in the front seat of the vehicle with a high degree of passive safety, particularly in accidents involving head-on collisions. According to the known art, however, should the occupants not use their seat belts, only the passenger will still have the supplemental protection of the air bag system in accidents occurring at speeds corresponding to the first lower threshold value S1. Because the driver's air bag is activated only if the higher threshold value S2 is reached, the driver is subjected to a significantly greater risk of injury than is the passenger, particularly when the driver's seat belt is not fastened, despite the existing air bag system. It would, therefore, be useful to let the air bag system trigger for the driver's side at speeds corresponding to the lower threshold value (S1), when the driver is not wearing a seat belt.
It is, therefore, an object of this invention to provide a passsive restraining system which allows triggering of an air bag system at either a first lower threshold value or a second higher threshold value as a function of whether the seat belts have been fastened or not.
It is further an object to provide a restraining system whereby even if the seat belt is not fastened, the driver as well as the passenger is protected by the air bag system at a low speed collision.
The above and other objects are attained by a passive restraining system of a vehicle which protects both the driver and front seat passenger in low speed collisions with the system comprising of an air bag system, a sensor, and a switching means. When the sensor detects a sudden change in the vehicle's speed as a result of an accident, it provides one of two output signals to the air bag system via a switching means. A first output signal is emitted when the vehicle speed had reached a first lower threshold value (S1), and a second output signal is emitted when the vehicle speed has reached a second higher threshold value (S2). The switching means determines which sensor signal is provided to the air bag system based upon whether the driver has fastened his seat belt or not. If he has not fastened it, the switching means provides a connection between the sensor's first output signal and the air bag system. If the driver has fastened his seat belt, the switching means then provides a connection between the sensor's second output signal and the air bag sytem. A switching means for detecting when a seat belt is fastened or not can be provided for any seat equipped with a passive restraining system.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing.